gammagoblin a dit:
As for ketamine vs dmt, I haven't smoked DMT so I can't really compare the two but I have heard someone talking about these substances and he said they both bring you to the same plane but through different roads. ie ketamine shutting of the signals, and DMT amplifying them to extreme proportions.
Yes, I heard something along those lines as well, but the same goes for this as I told Illegalsmile: It is not about the ketamine experience as a whole. Just the fact that ketamine directly blocks NMDA receptors (it is a NDMA receptor antagonist), and the supposed observation that people under the influence of ketamine report OBEs quite frequently (more than compared to other psychedelic substances). This combined with the knowledge that many 'natural circumstances' (such as epileptic seizures for example) that cause OBEs cause a flooding of the neurotransmitter glutamate in the brain, which also causes the brain to block NDMA receptors.
After reading the article by
Braithwaite et al. (2011) I have to say though, that this theory is probably wrong. As is stated in the article OBEs are also experienced quite regularly (relatively speaking of course) by 'normal', healthy people. Those people then would not experience such 'natural circumstances' and consequently would not have their brains flooded with glutamate, in turn causing no blockade of the NMDA receptors, unless there is some unkown factor which causes this blockade in those people. Maybe these people are predisposed to having low amounts of NMDA receptors, or have naturally occuring high levels of glutamate going around in their brains, or something else along those lines, thus making them more prone to OBEs.
gammagoblin a dit:
Interesting that there could be a specific part of the brain responsible for these kinds of experiences. This poses the question to me, is that part of the brain designed to produce such experiences or would it be because of overload in that specific area for example?
I do not think there is a specific brain region that is responsible for mystical experiences or alike. These experiences can take on various forms with differing emotional aspects, absence or presence of either auditory or visual hallucinations, can involve the future, the past or neither, involving only the here and now. I'd say any single combination of these, and any other features I didn't mention, would involve (at least in part) different regions of the brain in comparison to any other combination of features of the experience.
What probably is the case is that any specific feature of the experience, as opposed to the experience as a whole, is produced by a certain region of the brain. In the introductory section of the article by
Braithwaite et al. (2011) there is a short mentioning of the 'emerging view' in regard to how the "exocentral" perspective during an OBE is induced (i.e. how one can perceive one's surrounding from a different point of view than that of your own body/your eyes). It states that it is due to
"simultaneous breakdown in parietal networks sub-serving multi-sensory egocentric processing and medial temporal-lobe structures involved in exocentric perspective-taking".
To understand this you have to know that the parietal lobe is involved in integrating information from different sensorial modalities (touch, sound, vision etc.) to create a picture of the 'whole' experience. This whole experience is what you normally experience in everyday life. You rarely experience the world solely in terms of touch, or sound (etc.), unless of course you are tripping very hard or have some other experience like this. Actually I have read or heard somewhere that fMRI scans showed
less communication between different parts of the brain in people under the influence of some psychedelic substance (don't remember which; probably LSD or psilocybine/psilocyne). This could pretty much be boiled down to the same argument made in the first part of the quote about the breakdown in parietal networks. Anyway, back to the OBE: Due to the breakdown in the parietal networks in question, visual information and sensory feedback information from the body itself, such as the unconscious awareness of the location and positioning of the different parts or limbs of your body and how much effort is being used in moving these body parts (proprioceptive feedback) and the feeling of balance (vestibular feedback), is not integrated into a 'whole' picture. Still the brain has to give you
some kind of experience (it doesn't just "crash" like a computer would, giving you the blue screen of death or something
(unless you consider
this to be the "crash")). So it does the best it can with the information it has received and integrated to create a 'complete' experience. So the proprioceptive and vestibular feedback are not combined with the visual information coming in, resulting in a visual experience where you are
not in your body. It doesn't really matter where you are looking from, as long as it is not your body. From there on all kind of strange experiences can arise as your brain is trying really hard to make sense of things, keeping it as sensical as it possibly can with such strange incoherent sensorial information coming in.
Now, this theory, as far as I can tell, doesn't really combine well with the ketamine model of OBEs. Unless an NMDA receptor blockade might cause a breakdown of the parts of the parietal and temporal lobe mentioned before, but this doesn't fit very well with case reports of temporal lobe stimulation causing this kind of experiences. My guess is one of them is wrong, probably the ketamine model because of the reason mentioned at the start of this post.
EDIT: I wanted to say one more thing, as I can very well understand that all of this might look as if I am saying that these kind of experiences are nothing more than a 'damaged' or dyregulated brain trying to make sense of the world. I do not believe this is entirely the case. I believe there is quite some more value to these kind of experiences. They show us what the world is like outside of ordinary everyday life. I do not think that just because the brain works differently that all of a sudden it is any less real. I mean, what makes this specific configuration of our brains any more real than any of the (many) 'psychedelic' configurations? I believe a lot can be learnt from those experiences about the world. There is, in my opinion, a lot more to life than the undrugged and unaltered state of consciousness, which is just one aspect of reality, one way of experiencing reality, one "codec" if you like. But there are many more "codecs" which are just as real and meaningful, from which just as much if not more can be learnt. I even think it is
very important to make these other states of consciousness part of humanities 'reality-perspective' as it is pretty much impossible to
really understand ordinary reality without having something else to compare it to.
Ok, just had to mention that. While re-reading my post it came across kind of 'empty' and mechanical, but that's just the scientist in me talking.
